This algorithm is based on Vallado implementation, and does basic Newton
iteration on the Kepler equation written using universal variables. Battin
claims his algorithm uses the same amount of memory but is between 40 %
and 85 % faster.

This class holds the perifocal plane of the first
State plotted in it using
plot(), so all following
plots will be projected on that plane. Alternatively, you can call
set_frame() to set the frame before plotting.

This is just a convenience function around
astropy.coordinates.matrix_utilities.rotation_matrix().

Parameters:

vector (array_like) – Dimension 3 vector.

angle (convertible to Angle) – Angle of rotation.

axis (str or 3-sequence) – Either ‘x’,’y’, ‘z’, or a (x,y,z) specifying an axis to rotate
about. If ‘x’,’y’, or ‘z’, the rotation sense is
counterclockwise looking down the + axis (e.g. positive
rotations obey left-hand-rule).

unit (UnitBase, optional) – If angle does not have associated units, they are in this
unit. If neither are provided, it is assumed to be degrees.

Note

This is just a convenience function around
astropy.coordinates.matrix_utilities.rotation_matrix().
This performs a so-called active or alibi transformation: rotates the
vector while the coordinate system remains unchanged. To do the opposite
operation (passive or alias transformation) call the function as
rotate(vec,ax,-angle,unit) or use the convenience function
transform(), see [1].